net/mptcp/options.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* Multipath TCP
   3  *
   4  * Copyright (c) 2017 - 2019, Intel Corporation.
   5  */
   6
   7 #define pr_fmt(fmt) "MPTCP: " fmt
   8
   9 #include <linux/kernel.h>
  10 #include <crypto/sha2.h>
  11 #include <net/tcp.h>
  12 #include <net/mptcp.h>
  13 #include "protocol.h"
  14 #include "mib.h"
  15
  16 #include <trace/events/mptcp.h>
  17
  18 static bool mptcp_cap_flag_sha256(u8 flags)
  19 {
  20         return (flags & MPTCP_CAP_FLAG_MASK) == MPTCP_CAP_HMAC_SHA256;
  21 }
  22
  23 static void mptcp_parse_option(const struct sk_buff *skb,
  24                                const unsigned char *ptr, int opsize,
  25                                struct mptcp_options_received *mp_opt)
  26 {
  27         u8 subtype = *ptr >> 4;
  28         int expected_opsize;
  29         u16 subopt;
  30         u8 version;
  31         u8 flags;
  32         u8 i;
  33
  34         switch (subtype) {
  35         case MPTCPOPT_MP_CAPABLE:
  36                 /* strict size checking */
  37                 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
  38                         if (skb->len > tcp_hdr(skb)->doff << 2)
  39                                 expected_opsize = TCPOLEN_MPTCP_MPC_ACK_DATA;
  40                         else
  41                                 expected_opsize = TCPOLEN_MPTCP_MPC_ACK;
  42                         subopt = OPTION_MPTCP_MPC_ACK;
  43                 } else {
  44                         if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK) {
  45                                 expected_opsize = TCPOLEN_MPTCP_MPC_SYNACK;
  46                                 subopt = OPTION_MPTCP_MPC_SYNACK;
  47                         } else {
  48                                 expected_opsize = TCPOLEN_MPTCP_MPC_SYN;
  49                                 subopt = OPTION_MPTCP_MPC_SYN;
  50                         }
  51                 }
  52
  53                 /* Cfr RFC 8684 Section 3.3.0:
  54                  * If a checksum is present but its use had
  55                  * not been negotiated in the MP_CAPABLE handshake, the receiver MUST
  56                  * close the subflow with a RST, as it is not behaving as negotiated.
  57                  * If a checksum is not present when its use has been negotiated, the
  58                  * receiver MUST close the subflow with a RST, as it is considered
  59                  * broken
  60                  * We parse even option with mismatching csum presence, so that
  61                  * later in subflow_data_ready we can trigger the reset.
  62                  */
  63                 if (opsize != expected_opsize &&
  64                     (expected_opsize != TCPOLEN_MPTCP_MPC_ACK_DATA ||
  65                      opsize != TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM))
  66                         break;
  67
  68                 /* try to be gentle vs future versions on the initial syn */
  69                 version = *ptr++ & MPTCP_VERSION_MASK;
  70                 if (opsize != TCPOLEN_MPTCP_MPC_SYN) {
  71                         if (version != MPTCP_SUPPORTED_VERSION)
  72                                 break;
  73                 } else if (version < MPTCP_SUPPORTED_VERSION) {
  74                         break;
  75                 }
  76
  77                 flags = *ptr++;
  78                 if (!mptcp_cap_flag_sha256(flags) ||
  79                     (flags & MPTCP_CAP_EXTENSIBILITY))
  80                         break;
  81
  82                 /* RFC 6824, Section 3.1:
  83                  * "For the Checksum Required bit (labeled "A"), if either
  84                  * host requires the use of checksums, checksums MUST be used.
  85                  * In other words, the only way for checksums not to be used
  86                  * is if both hosts in their SYNs set A=0."
  87                  */
  88                 if (flags & MPTCP_CAP_CHECKSUM_REQD)
  89                         mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
  90
  91                 mp_opt->deny_join_id0 = !!(flags & MPTCP_CAP_DENY_JOIN_ID0);
  92
  93                 mp_opt->suboptions |= subopt;
  94                 if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) {
  95                         mp_opt->sndr_key = get_unaligned_be64(ptr);
  96                         ptr += 8;
  97                 }
  98                 if (opsize >= TCPOLEN_MPTCP_MPC_ACK) {
  99                         mp_opt->rcvr_key = get_unaligned_be64(ptr);
 100                         ptr += 8;
 101                 }
 102                 if (opsize >= TCPOLEN_MPTCP_MPC_ACK_DATA) {
 103                         /* Section 3.1.:
 104                          * "the data parameters in a MP_CAPABLE are semantically
 105                          * equivalent to those in a DSS option and can be used
 106                          * interchangeably."
 107                          */
 108                         mp_opt->suboptions |= OPTION_MPTCP_DSS;
 109                         mp_opt->use_map = 1;
 110                         mp_opt->mpc_map = 1;
 111                         mp_opt->use_ack = 0;
 112                         mp_opt->data_len = get_unaligned_be16(ptr);
 113                         ptr += 2;
 114                 }
 115                 if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM) {
 116                         mp_opt->csum = get_unaligned((__force __sum16 *)ptr);
 117                         mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
 118                         ptr += 2;
 119                 }
 120                 pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d csum=%u",
 121                          version, flags, opsize, mp_opt->sndr_key,
 122                          mp_opt->rcvr_key, mp_opt->data_len, mp_opt->csum);
 123                 break;
 124
 125         case MPTCPOPT_MP_JOIN:
 126                 if (opsize == TCPOLEN_MPTCP_MPJ_SYN) {
 127                         mp_opt->suboptions |= OPTION_MPTCP_MPJ_SYN;
 128                         mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 129                         mp_opt->join_id = *ptr++;
 130                         mp_opt->token = get_unaligned_be32(ptr);
 131                         ptr += 4;
 132                         mp_opt->nonce = get_unaligned_be32(ptr);
 133                         ptr += 4;
 134                         pr_debug("MP_JOIN bkup=%u, id=%u, token=%u, nonce=%u",
 135                                  mp_opt->backup, mp_opt->join_id,
 136                                  mp_opt->token, mp_opt->nonce);
 137                 } else if (opsize == TCPOLEN_MPTCP_MPJ_SYNACK) {
 138                         mp_opt->suboptions |= OPTION_MPTCP_MPJ_SYNACK;
 139                         mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 140                         mp_opt->join_id = *ptr++;
 141                         mp_opt->thmac = get_unaligned_be64(ptr);
 142                         ptr += 8;
 143                         mp_opt->nonce = get_unaligned_be32(ptr);
 144                         ptr += 4;
 145                         pr_debug("MP_JOIN bkup=%u, id=%u, thmac=%llu, nonce=%u",
 146                                  mp_opt->backup, mp_opt->join_id,
 147                                  mp_opt->thmac, mp_opt->nonce);
 148                 } else if (opsize == TCPOLEN_MPTCP_MPJ_ACK) {
 149                         mp_opt->suboptions |= OPTION_MPTCP_MPJ_ACK;
 150                         ptr += 2;
 151                         memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN);
 152                         pr_debug("MP_JOIN hmac");
 153                 }
 154                 break;
 155
 156         case MPTCPOPT_DSS:
 157                 pr_debug("DSS");
 158                 ptr++;
 159
 160                 /* we must clear 'mpc_map' be able to detect MP_CAPABLE
 161                  * map vs DSS map in mptcp_incoming_options(), and reconstruct
 162                  * map info accordingly
 163                  */
 164                 mp_opt->mpc_map = 0;
 165                 flags = (*ptr++) & MPTCP_DSS_FLAG_MASK;
 166                 mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0;
 167                 mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0;
 168                 mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0;
 169                 mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0;
 170                 mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK);
 171
 172                 pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d",
 173                          mp_opt->data_fin, mp_opt->dsn64,
 174                          mp_opt->use_map, mp_opt->ack64,
 175                          mp_opt->use_ack);
 176
 177                 expected_opsize = TCPOLEN_MPTCP_DSS_BASE;
 178
 179                 if (mp_opt->use_ack) {
 180                         if (mp_opt->ack64)
 181                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK64;
 182                         else
 183                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK32;
 184                 }
 185
 186                 if (mp_opt->use_map) {
 187                         if (mp_opt->dsn64)
 188                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP64;
 189                         else
 190                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP32;
 191                 }
 192
 193                 /* Always parse any csum presence combination, we will enforce
 194                  * RFC 8684 Section 3.3.0 checks later in subflow_data_ready
 195                  */
 196                 if (opsize != expected_opsize &&
 197                     opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM)
 198                         break;
 199
 200                 mp_opt->suboptions |= OPTION_MPTCP_DSS;
 201                 if (mp_opt->use_ack) {
 202                         if (mp_opt->ack64) {
 203                                 mp_opt->data_ack = get_unaligned_be64(ptr);
 204                                 ptr += 8;
 205                         } else {
 206                                 mp_opt->data_ack = get_unaligned_be32(ptr);
 207                                 ptr += 4;
 208                         }
 209
 210                         pr_debug("data_ack=%llu", mp_opt->data_ack);
 211                 }
 212
 213                 if (mp_opt->use_map) {
 214                         if (mp_opt->dsn64) {
 215                                 mp_opt->data_seq = get_unaligned_be64(ptr);
 216                                 ptr += 8;
 217                         } else {
 218                                 mp_opt->data_seq = get_unaligned_be32(ptr);
 219                                 ptr += 4;
 220                         }
 221
 222                         mp_opt->subflow_seq = get_unaligned_be32(ptr);
 223                         ptr += 4;
 224
 225                         mp_opt->data_len = get_unaligned_be16(ptr);
 226                         ptr += 2;
 227
 228                         if (opsize == expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM) {
 229                                 mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
 230                                 mp_opt->csum = get_unaligned((__force __sum16 *)ptr);
 231                                 ptr += 2;
 232                         }
 233
 234                         pr_debug("data_seq=%llu subflow_seq=%u data_len=%u csum=%d:%u",
 235                                  mp_opt->data_seq, mp_opt->subflow_seq,
 236                                  mp_opt->data_len, !!(mp_opt->suboptions & OPTION_MPTCP_CSUMREQD),
 237                                  mp_opt->csum);
 238                 }
 239
 240                 break;
 241
 242         case MPTCPOPT_ADD_ADDR:
 243                 mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO;
 244                 if (!mp_opt->echo) {
 245                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR ||
 246                             opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT)
 247                                 mp_opt->addr.family = AF_INET;
 248 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 249                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6 ||
 250                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT)
 251                                 mp_opt->addr.family = AF_INET6;
 252 #endif
 253                         else
 254                                 break;
 255                 } else {
 256                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE ||
 257                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT)
 258                                 mp_opt->addr.family = AF_INET;
 259 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 260                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE ||
 261                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT)
 262                                 mp_opt->addr.family = AF_INET6;
 263 #endif
 264                         else
 265                                 break;
 266                 }
 267
 268                 mp_opt->suboptions |= OPTION_MPTCP_ADD_ADDR;
 269                 mp_opt->addr.id = *ptr++;
 270                 mp_opt->addr.port = 0;
 271                 mp_opt->ahmac = 0;
 272                 if (mp_opt->addr.family == AF_INET) {
 273                         memcpy((u8 *)&mp_opt->addr.addr.s_addr, (u8 *)ptr, 4);
 274                         ptr += 4;
 275                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT ||
 276                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) {
 277                                 mp_opt->addr.port = htons(get_unaligned_be16(ptr));
 278                                 ptr += 2;
 279                         }
 280                 }
 281 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 282                 else {
 283                         memcpy(mp_opt->addr.addr6.s6_addr, (u8 *)ptr, 16);
 284                         ptr += 16;
 285                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT ||
 286                             opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) {
 287                                 mp_opt->addr.port = htons(get_unaligned_be16(ptr));
 288                                 ptr += 2;
 289                         }
 290                 }
 291 #endif
 292                 if (!mp_opt->echo) {
 293                         mp_opt->ahmac = get_unaligned_be64(ptr);
 294                         ptr += 8;
 295                 }
 296                 pr_debug("ADD_ADDR%s: id=%d, ahmac=%llu, echo=%d, port=%d",
 297                          (mp_opt->addr.family == AF_INET6) ? "6" : "",
 298                          mp_opt->addr.id, mp_opt->ahmac, mp_opt->echo, ntohs(mp_opt->addr.port));
 299                 break;
 300
 301         case MPTCPOPT_RM_ADDR:
 302                 if (opsize < TCPOLEN_MPTCP_RM_ADDR_BASE + 1 ||
 303                     opsize > TCPOLEN_MPTCP_RM_ADDR_BASE + MPTCP_RM_IDS_MAX)
 304                         break;
 305
 306                 ptr++;
 307
 308                 mp_opt->suboptions |= OPTION_MPTCP_RM_ADDR;
 309                 mp_opt->rm_list.nr = opsize - TCPOLEN_MPTCP_RM_ADDR_BASE;
 310                 for (i = 0; i < mp_opt->rm_list.nr; i++)
 311                         mp_opt->rm_list.ids[i] = *ptr++;
 312                 pr_debug("RM_ADDR: rm_list_nr=%d", mp_opt->rm_list.nr);
 313                 break;
 314
 315         case MPTCPOPT_MP_PRIO:
 316                 if (opsize != TCPOLEN_MPTCP_PRIO)
 317                         break;
 318
 319                 mp_opt->suboptions |= OPTION_MPTCP_PRIO;
 320                 mp_opt->backup = *ptr++ & MPTCP_PRIO_BKUP;
 321                 pr_debug("MP_PRIO: prio=%d", mp_opt->backup);
 322                 break;
 323
 324         case MPTCPOPT_MP_FASTCLOSE:
 325                 if (opsize != TCPOLEN_MPTCP_FASTCLOSE)
 326                         break;
 327
 328                 ptr += 2;
 329                 mp_opt->rcvr_key = get_unaligned_be64(ptr);
 330                 ptr += 8;
 331                 mp_opt->suboptions |= OPTION_MPTCP_FASTCLOSE;
 332                 pr_debug("MP_FASTCLOSE: recv_key=%llu", mp_opt->rcvr_key);
 333                 break;
 334
 335         case MPTCPOPT_RST:
 336                 if (opsize != TCPOLEN_MPTCP_RST)
 337                         break;
 338
 339                 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST))
 340                         break;
 341
 342                 mp_opt->suboptions |= OPTION_MPTCP_RST;
 343                 flags = *ptr++;
 344                 mp_opt->reset_transient = flags & MPTCP_RST_TRANSIENT;
 345                 mp_opt->reset_reason = *ptr;
 346                 pr_debug("MP_RST: transient=%u reason=%u",
 347                          mp_opt->reset_transient, mp_opt->reset_reason);
 348                 break;
 349
 350         case MPTCPOPT_MP_FAIL:
 351                 if (opsize != TCPOLEN_MPTCP_FAIL)
 352                         break;
 353
 354                 ptr += 2;
 355                 mp_opt->suboptions |= OPTION_MPTCP_FAIL;
 356                 mp_opt->fail_seq = get_unaligned_be64(ptr);
 357                 pr_debug("MP_FAIL: data_seq=%llu", mp_opt->fail_seq);
 358                 break;
 359
 360         default:
 361                 break;
 362         }
 363 }
 364
 365 void mptcp_get_options(const struct sk_buff *skb,
 366                        struct mptcp_options_received *mp_opt)
 367 {
 368         const struct tcphdr *th = tcp_hdr(skb);
 369         const unsigned char *ptr;
 370         int length;
 371
 372         /* initialize option status */
 373         mp_opt->suboptions = 0;
 374
 375         length = (th->doff * 4) - sizeof(struct tcphdr);
 376         ptr = (const unsigned char *)(th + 1);
 377
 378         while (length > 0) {
 379                 int opcode = *ptr++;
 380                 int opsize;
 381
 382                 switch (opcode) {
 383                 case TCPOPT_EOL:
 384                         return;
 385                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 386                         length--;
 387                         continue;
 388                 default:
 389                         if (length < 2)
 390                                 return;
 391                         opsize = *ptr++;
 392                         if (opsize < 2) /* "silly options" */
 393                                 return;
 394                         if (opsize > length)
 395                                 return; /* don't parse partial options */
 396                         if (opcode == TCPOPT_MPTCP)
 397                                 mptcp_parse_option(skb, ptr, opsize, mp_opt);
 398                         ptr += opsize - 2;
 399                         length -= opsize;
 400                 }
 401         }
 402 }
 403
 404 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 405                        unsigned int *size, struct mptcp_out_options *opts)
 406 {
 407         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 408
 409         /* we will use snd_isn to detect first pkt [re]transmission
 410          * in mptcp_established_options_mp()
 411          */
 412         subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
 413         if (subflow->request_mptcp) {
 414                 opts->suboptions = OPTION_MPTCP_MPC_SYN;
 415                 opts->csum_reqd = mptcp_is_checksum_enabled(sock_net(sk));
 416                 opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
 417                 *size = TCPOLEN_MPTCP_MPC_SYN;
 418                 return true;
 419         } else if (subflow->request_join) {
 420                 pr_debug("remote_token=%u, nonce=%u", subflow->remote_token,
 421                          subflow->local_nonce);
 422                 opts->suboptions = OPTION_MPTCP_MPJ_SYN;
 423                 opts->join_id = subflow->local_id;
 424                 opts->token = subflow->remote_token;
 425                 opts->nonce = subflow->local_nonce;
 426                 opts->backup = subflow->request_bkup;
 427                 *size = TCPOLEN_MPTCP_MPJ_SYN;
 428                 return true;
 429         }
 430         return false;
 431 }
 432
 433 static void clear_3rdack_retransmission(struct sock *sk)
 434 {
 435         struct inet_connection_sock *icsk = inet_csk(sk);
 436
 437         sk_stop_timer(sk, &icsk->icsk_delack_timer);
 438         icsk->icsk_ack.timeout = 0;
 439         icsk->icsk_ack.ato = 0;
 440         icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
 441 }
 442
 443 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 444                                          bool snd_data_fin_enable,
 445                                          unsigned int *size,
 446                                          struct mptcp_out_options *opts)
 447 {
 448         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 449         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 450         struct mptcp_ext *mpext;
 451         unsigned int data_len;
 452         u8 len;
 453
 454         /* When skb is not available, we better over-estimate the emitted
 455          * options len. A full DSS option (28 bytes) is longer than
 456          * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
 457          * tell the caller to defer the estimate to
 458          * mptcp_established_options_dss(), which will reserve enough space.
 459          */
 460         if (!skb)
 461                 return false;
 462
 463         /* MPC/MPJ needed only on 3rd ack packet, DATA_FIN and TCP shutdown take precedence */
 464         if (subflow->fully_established || snd_data_fin_enable ||
 465             subflow->snd_isn != TCP_SKB_CB(skb)->seq ||
 466             sk->sk_state != TCP_ESTABLISHED)
 467                 return false;
 468
 469         if (subflow->mp_capable) {
 470                 mpext = mptcp_get_ext(skb);
 471                 data_len = mpext ? mpext->data_len : 0;
 472
 473                 /* we will check ops->data_len in mptcp_write_options() to
 474                  * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
 475                  * TCPOLEN_MPTCP_MPC_ACK
 476                  */
 477                 opts->data_len = data_len;
 478                 opts->suboptions = OPTION_MPTCP_MPC_ACK;
 479                 opts->sndr_key = subflow->local_key;
 480                 opts->rcvr_key = subflow->remote_key;
 481                 opts->csum_reqd = READ_ONCE(msk->csum_enabled);
 482                 opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
 483
 484                 /* Section 3.1.
 485                  * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
 486                  * packets that start the first subflow of an MPTCP connection,
 487                  * as well as the first packet that carries data
 488                  */
 489                 if (data_len > 0) {
 490                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
 491                         if (opts->csum_reqd) {
 492                                 /* we need to propagate more info to csum the pseudo hdr */
 493                                 opts->data_seq = mpext->data_seq;
 494                                 opts->subflow_seq = mpext->subflow_seq;
 495                                 opts->csum = mpext->csum;
 496                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
 497                         }
 498                         *size = ALIGN(len, 4);
 499                 } else {
 500                         *size = TCPOLEN_MPTCP_MPC_ACK;
 501                 }
 502
 503                 pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d",
 504                          subflow, subflow->local_key, subflow->remote_key,
 505                          data_len);
 506
 507                 return true;
 508         } else if (subflow->mp_join) {
 509                 opts->suboptions = OPTION_MPTCP_MPJ_ACK;
 510                 memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
 511                 *size = TCPOLEN_MPTCP_MPJ_ACK;
 512                 pr_debug("subflow=%p", subflow);
 513
 514                 /* we can use the full delegate action helper only from BH context
 515                  * If we are in process context - sk is flushing the backlog at
 516                  * socket lock release time - just set the appropriate flag, will
 517                  * be handled by the release callback
 518                  */
 519                 if (sock_owned_by_user(sk))
 520                         set_bit(MPTCP_DELEGATE_ACK, &subflow->delegated_status);
 521                 else
 522                         mptcp_subflow_delegate(subflow, MPTCP_DELEGATE_ACK);
 523                 return true;
 524         }
 525         return false;
 526 }
 527
 528 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
 529                                  struct sk_buff *skb, struct mptcp_ext *ext)
 530 {
 531         /* The write_seq value has already been incremented, so the actual
 532          * sequence number for the DATA_FIN is one less.
 533          */
 534         u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1;
 535
 536         if (!ext->use_map || !skb->len) {
 537                 /* RFC6824 requires a DSS mapping with specific values
 538                  * if DATA_FIN is set but no data payload is mapped
 539                  */
 540                 ext->data_fin = 1;
 541                 ext->use_map = 1;
 542                 ext->dsn64 = 1;
 543                 ext->data_seq = data_fin_tx_seq;
 544                 ext->subflow_seq = 0;
 545                 ext->data_len = 1;
 546         } else if (ext->data_seq + ext->data_len == data_fin_tx_seq) {
 547                 /* If there's an existing DSS mapping and it is the
 548                  * final mapping, DATA_FIN consumes 1 additional byte of
 549                  * mapping space.
 550                  */
 551                 ext->data_fin = 1;
 552                 ext->data_len++;
 553         }
 554 }
 555
 556 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 557                                           bool snd_data_fin_enable,
 558                                           unsigned int *size,
 559                                           struct mptcp_out_options *opts)
 560 {
 561         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 562         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 563         unsigned int dss_size = 0;
 564         struct mptcp_ext *mpext;
 565         unsigned int ack_size;
 566         bool ret = false;
 567         u64 ack_seq;
 568
 569         opts->csum_reqd = READ_ONCE(msk->csum_enabled);
 570         mpext = skb ? mptcp_get_ext(skb) : NULL;
 571
 572         if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
 573                 unsigned int map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
 574
 575                 if (mpext) {
 576                         if (opts->csum_reqd)
 577                                 map_size += TCPOLEN_MPTCP_DSS_CHECKSUM;
 578
 579                         opts->ext_copy = *mpext;
 580                 }
 581
 582                 dss_size = map_size;
 583                 if (skb && snd_data_fin_enable)
 584                         mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
 585                 opts->suboptions = OPTION_MPTCP_DSS;
 586                 ret = true;
 587         }
 588
 589         /* passive sockets msk will set the 'can_ack' after accept(), even
 590          * if the first subflow may have the already the remote key handy
 591          */
 592         opts->ext_copy.use_ack = 0;
 593         if (!READ_ONCE(msk->can_ack)) {
 594                 *size = ALIGN(dss_size, 4);
 595                 return ret;
 596         }
 597
 598         ack_seq = READ_ONCE(msk->ack_seq);
 599         if (READ_ONCE(msk->use_64bit_ack)) {
 600                 ack_size = TCPOLEN_MPTCP_DSS_ACK64;
 601                 opts->ext_copy.data_ack = ack_seq;
 602                 opts->ext_copy.ack64 = 1;
 603         } else {
 604                 ack_size = TCPOLEN_MPTCP_DSS_ACK32;
 605                 opts->ext_copy.data_ack32 = (uint32_t)ack_seq;
 606                 opts->ext_copy.ack64 = 0;
 607         }
 608         opts->ext_copy.use_ack = 1;
 609         opts->suboptions = OPTION_MPTCP_DSS;
 610         WRITE_ONCE(msk->old_wspace, __mptcp_space((struct sock *)msk));
 611
 612         /* Add kind/length/subtype/flag overhead if mapping is not populated */
 613         if (dss_size == 0)
 614                 ack_size += TCPOLEN_MPTCP_DSS_BASE;
 615
 616         dss_size += ack_size;
 617
 618         *size = ALIGN(dss_size, 4);
 619         return true;
 620 }
 621
 622 static u64 add_addr_generate_hmac(u64 key1, u64 key2,
 623                                   struct mptcp_addr_info *addr)
 624 {
 625         u16 port = ntohs(addr->port);
 626         u8 hmac[SHA256_DIGEST_SIZE];
 627         u8 msg[19];
 628         int i = 0;
 629
 630         msg[i++] = addr->id;
 631         if (addr->family == AF_INET) {
 632                 memcpy(&msg[i], &addr->addr.s_addr, 4);
 633                 i += 4;
 634         }
 635 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 636         else if (addr->family == AF_INET6) {
 637                 memcpy(&msg[i], &addr->addr6.s6_addr, 16);
 638                 i += 16;
 639         }
 640 #endif
 641         msg[i++] = port >> 8;
 642         msg[i++] = port & 0xFF;
 643
 644         mptcp_crypto_hmac_sha(key1, key2, msg, i, hmac);
 645
 646         return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
 647 }
 648
 649 static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *skb,
 650                                                unsigned int *size,
 651                                                unsigned int remaining,
 652                                                struct mptcp_out_options *opts)
 653 {
 654         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 655         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 656         bool drop_other_suboptions = false;
 657         unsigned int opt_size = *size;
 658         bool echo;
 659         int len;
 660
 661         /* add addr will strip the existing options, be sure to avoid breaking
 662          * MPC/MPJ handshakes
 663          */
 664         if (!mptcp_pm_should_add_signal(msk) ||
 665             (opts->suboptions & (OPTION_MPTCP_MPJ_ACK | OPTION_MPTCP_MPC_ACK)) ||
 666             !mptcp_pm_add_addr_signal(msk, skb, opt_size, remaining, &opts->addr,
 667                     &echo, &drop_other_suboptions))
 668                 return false;
 669
 670         if (drop_other_suboptions)
 671                 remaining += opt_size;
 672         len = mptcp_add_addr_len(opts->addr.family, echo, !!opts->addr.port);
 673         if (remaining < len)
 674                 return false;
 675
 676         *size = len;
 677         if (drop_other_suboptions) {
 678                 pr_debug("drop other suboptions");
 679                 opts->suboptions = 0;
 680
 681                 /* note that e.g. DSS could have written into the memory
 682                  * aliased by ahmac, we must reset the field here
 683                  * to avoid appending the hmac even for ADD_ADDR echo
 684                  * options
 685                  */
 686                 opts->ahmac = 0;
 687                 *size -= opt_size;
 688         }
 689         opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
 690         if (!echo) {
 691                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDRTX);
 692                 opts->ahmac = add_addr_generate_hmac(msk->local_key,
 693                                                      msk->remote_key,
 694                                                      &opts->addr);
 695         } else {
 696                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADDTX);
 697         }
 698         pr_debug("addr_id=%d, ahmac=%llu, echo=%d, port=%d",
 699                  opts->addr.id, opts->ahmac, echo, ntohs(opts->addr.port));
 700
 701         return true;
 702 }
 703
 704 static bool mptcp_established_options_rm_addr(struct sock *sk,
 705                                               unsigned int *size,
 706                                               unsigned int remaining,
 707                                               struct mptcp_out_options *opts)
 708 {
 709         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 710         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 711         struct mptcp_rm_list rm_list;
 712         int i, len;
 713
 714         if (!mptcp_pm_should_rm_signal(msk) ||
 715             !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_list)))
 716                 return false;
 717
 718         len = mptcp_rm_addr_len(&rm_list);
 719         if (len < 0)
 720                 return false;
 721         if (remaining < len)
 722                 return false;
 723
 724         *size = len;
 725         opts->suboptions |= OPTION_MPTCP_RM_ADDR;
 726         opts->rm_list = rm_list;
 727
 728         for (i = 0; i < opts->rm_list.nr; i++)
 729                 pr_debug("rm_list_ids[%d]=%d", i, opts->rm_list.ids[i]);
 730         MPTCP_ADD_STATS(sock_net(sk), MPTCP_MIB_RMADDRTX, opts->rm_list.nr);
 731         return true;
 732 }
 733
 734 static bool mptcp_established_options_mp_prio(struct sock *sk,
 735                                               unsigned int *size,
 736                                               unsigned int remaining,
 737                                               struct mptcp_out_options *opts)
 738 {
 739         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 740
 741         /* can't send MP_PRIO with MPC, as they share the same option space:
 742          * 'backup'. Also it makes no sense at all
 743          */
 744         if (!subflow->send_mp_prio || (opts->suboptions & OPTIONS_MPTCP_MPC))
 745                 return false;
 746
 747         /* account for the trailing 'nop' option */
 748         if (remaining < TCPOLEN_MPTCP_PRIO_ALIGN)
 749                 return false;
 750
 751         *size = TCPOLEN_MPTCP_PRIO_ALIGN;
 752         opts->suboptions |= OPTION_MPTCP_PRIO;
 753         opts->backup = subflow->request_bkup;
 754
 755         pr_debug("prio=%d", opts->backup);
 756
 757         return true;
 758 }
 759
 760 static noinline bool mptcp_established_options_rst(struct sock *sk, struct sk_buff *skb,
 761                                                    unsigned int *size,
 762                                                    unsigned int remaining,
 763                                                    struct mptcp_out_options *opts)
 764 {
 765         const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 766
 767         if (remaining < TCPOLEN_MPTCP_RST)
 768                 return false;
 769
 770         *size = TCPOLEN_MPTCP_RST;
 771         opts->suboptions |= OPTION_MPTCP_RST;
 772         opts->reset_transient = subflow->reset_transient;
 773         opts->reset_reason = subflow->reset_reason;
 774         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPRSTTX);
 775
 776         return true;
 777 }
 778
 779 static bool mptcp_established_options_fastclose(struct sock *sk,
 780                                                 unsigned int *size,
 781                                                 unsigned int remaining,
 782                                                 struct mptcp_out_options *opts)
 783 {
 784         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 785         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 786
 787         if (likely(!subflow->send_fastclose))
 788                 return false;
 789
 790         if (remaining < TCPOLEN_MPTCP_FASTCLOSE)
 791                 return false;
 792
 793         *size = TCPOLEN_MPTCP_FASTCLOSE;
 794         opts->suboptions |= OPTION_MPTCP_FASTCLOSE;
 795         opts->rcvr_key = msk->remote_key;
 796
 797         pr_debug("FASTCLOSE key=%llu", opts->rcvr_key);
 798         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFASTCLOSETX);
 799         return true;
 800 }
 801
 802 static bool mptcp_established_options_mp_fail(struct sock *sk,
 803                                               unsigned int *size,
 804                                               unsigned int remaining,
 805                                               struct mptcp_out_options *opts)
 806 {
 807         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 808
 809         if (likely(!subflow->send_mp_fail))
 810                 return false;
 811
 812         if (remaining < TCPOLEN_MPTCP_FAIL)
 813                 return false;
 814
 815         *size = TCPOLEN_MPTCP_FAIL;
 816         opts->suboptions |= OPTION_MPTCP_FAIL;
 817         opts->fail_seq = subflow->map_seq;
 818
 819         pr_debug("MP_FAIL fail_seq=%llu", opts->fail_seq);
 820         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILTX);
 821
 822         return true;
 823 }
 824
 825 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 826                                unsigned int *size, unsigned int remaining,
 827                                struct mptcp_out_options *opts)
 828 {
 829         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 830         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 831         unsigned int opt_size = 0;
 832         bool snd_data_fin;
 833         bool ret = false;
 834
 835         opts->suboptions = 0;
 836
 837         if (unlikely(__mptcp_check_fallback(msk) && !mptcp_check_infinite_map(skb)))
 838                 return false;
 839
 840         if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) {
 841                 if (mptcp_established_options_fastclose(sk, &opt_size, remaining, opts) ||
 842                     mptcp_established_options_mp_fail(sk, &opt_size, remaining, opts)) {
 843                         *size += opt_size;
 844                         remaining -= opt_size;
 845                 }
 846                 /* MP_RST can be used with MP_FASTCLOSE and MP_FAIL if there is room */
 847                 if (mptcp_established_options_rst(sk, skb, &opt_size, remaining, opts)) {
 848                         *size += opt_size;
 849                         remaining -= opt_size;
 850                 }
 851                 return true;
 852         }
 853
 854         snd_data_fin = mptcp_data_fin_enabled(msk);
 855         if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, opts))
 856                 ret = true;
 857         else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, opts)) {
 858                 unsigned int mp_fail_size;
 859
 860                 ret = true;
 861                 if (mptcp_established_options_mp_fail(sk, &mp_fail_size,
 862                                                       remaining - opt_size, opts)) {
 863                         *size += opt_size + mp_fail_size;
 864                         remaining -= opt_size - mp_fail_size;
 865                         return true;
 866                 }
 867         }
 868
 869         /* we reserved enough space for the above options, and exceeding the
 870          * TCP option space would be fatal
 871          */
 872         if (WARN_ON_ONCE(opt_size > remaining))
 873                 return false;
 874
 875         *size += opt_size;
 876         remaining -= opt_size;
 877         if (mptcp_established_options_add_addr(sk, skb, &opt_size, remaining, opts)) {
 878                 *size += opt_size;
 879                 remaining -= opt_size;
 880                 ret = true;
 881         } else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) {
 882                 *size += opt_size;
 883                 remaining -= opt_size;
 884                 ret = true;
 885         }
 886
 887         if (mptcp_established_options_mp_prio(sk, &opt_size, remaining, opts)) {
 888                 *size += opt_size;
 889                 remaining -= opt_size;
 890                 ret = true;
 891         }
 892
 893         return ret;
 894 }
 895
 896 bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
 897                           struct mptcp_out_options *opts)
 898 {
 899         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 900
 901         if (subflow_req->mp_capable) {
 902                 opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
 903                 opts->sndr_key = subflow_req->local_key;
 904                 opts->csum_reqd = subflow_req->csum_reqd;
 905                 opts->allow_join_id0 = subflow_req->allow_join_id0;
 906                 *size = TCPOLEN_MPTCP_MPC_SYNACK;
 907                 pr_debug("subflow_req=%p, local_key=%llu",
 908                          subflow_req, subflow_req->local_key);
 909                 return true;
 910         } else if (subflow_req->mp_join) {
 911                 opts->suboptions = OPTION_MPTCP_MPJ_SYNACK;
 912                 opts->backup = subflow_req->backup;
 913                 opts->join_id = subflow_req->local_id;
 914                 opts->thmac = subflow_req->thmac;
 915                 opts->nonce = subflow_req->local_nonce;
 916                 pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u",
 917                          subflow_req, opts->backup, opts->join_id,
 918                          opts->thmac, opts->nonce);
 919                 *size = TCPOLEN_MPTCP_MPJ_SYNACK;
 920                 return true;
 921         }
 922         return false;
 923 }
 924
 925 static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 926                                     struct mptcp_subflow_context *subflow,
 927                                     struct sk_buff *skb,
 928                                     struct mptcp_options_received *mp_opt)
 929 {
 930         /* here we can process OoO, in-window pkts, only in-sequence 4th ack
 931          * will make the subflow fully established
 932          */
 933         if (likely(subflow->fully_established)) {
 934                 /* on passive sockets, check for 3rd ack retransmission
 935                  * note that msk is always set by subflow_syn_recv_sock()
 936                  * for mp_join subflows
 937                  */
 938                 if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
 939                     TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
 940                     subflow->mp_join && (mp_opt->suboptions & OPTIONS_MPTCP_MPJ) &&
 941                     !subflow->request_join)
 942                         tcp_send_ack(ssk);
 943                 goto check_notify;
 944         }
 945
 946         /* we must process OoO packets before the first subflow is fully
 947          * established. OoO packets are instead a protocol violation
 948          * for MP_JOIN subflows as the peer must not send any data
 949          * before receiving the forth ack - cfr. RFC 8684 section 3.2.
 950          */
 951         if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) {
 952                 if (subflow->mp_join)
 953                         goto reset;
 954                 if (subflow->is_mptfo && mp_opt->suboptions & OPTION_MPTCP_MPC_ACK)
 955                         goto set_fully_established;
 956                 return subflow->mp_capable;
 957         }
 958
 959         if (subflow->remote_key_valid &&
 960             (((mp_opt->suboptions & OPTION_MPTCP_DSS) && mp_opt->use_ack) ||
 961              ((mp_opt->suboptions & OPTION_MPTCP_ADD_ADDR) && !mp_opt->echo))) {
 962                 /* subflows are fully established as soon as we get any
 963                  * additional ack, including ADD_ADDR.
 964                  */
 965                 goto set_fully_established;
 966         }
 967
 968         /* If the first established packet does not contain MP_CAPABLE + data
 969          * then fallback to TCP. Fallback scenarios requires a reset for
 970          * MP_JOIN subflows.
 971          */
 972         if (!(mp_opt->suboptions & OPTIONS_MPTCP_MPC)) {
 973                 if (subflow->mp_join)
 974                         goto reset;
 975                 subflow->mp_capable = 0;
 976                 pr_fallback(msk);
 977                 mptcp_do_fallback(ssk);
 978                 return false;
 979         }
 980
 981         if (mp_opt->deny_join_id0)
 982                 WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
 983
 984         if (unlikely(!READ_ONCE(msk->pm.server_side)))
 985                 pr_warn_once("bogus mpc option on established client sk");
 986
 987 set_fully_established:
 988         mptcp_data_lock((struct sock *)msk);
 989         __mptcp_subflow_fully_established(msk, subflow, mp_opt);
 990         mptcp_data_unlock((struct sock *)msk);
 991
 992 check_notify:
 993         /* if the subflow is not already linked into the conn_list, we can't
 994          * notify the PM: this subflow is still on the listener queue
 995          * and the PM possibly acquiring the subflow lock could race with
 996          * the listener close
 997          */
 998         if (likely(subflow->pm_notified) || list_empty(&subflow->node))
 999                 return true;
1000
1001         subflow->pm_notified = 1;
1002         if (subflow->mp_join) {
1003                 clear_3rdack_retransmission(ssk);
1004                 mptcp_pm_subflow_established(msk);
1005         } else {
1006                 mptcp_pm_fully_established(msk, ssk);
1007         }
1008         return true;
1009
1010 reset:
1011         mptcp_subflow_reset(ssk);
1012         return false;
1013 }
1014
1015 u64 __mptcp_expand_seq(u64 old_seq, u64 cur_seq)
1016 {
1017         u32 old_seq32, cur_seq32;
1018
1019         old_seq32 = (u32)old_seq;
1020         cur_seq32 = (u32)cur_seq;
1021         cur_seq = (old_seq & GENMASK_ULL(63, 32)) + cur_seq32;
1022         if (unlikely(cur_seq32 < old_seq32 && before(old_seq32, cur_seq32)))
1023                 return cur_seq + (1LL << 32);
1024
1025         /* reverse wrap could happen, too */
1026         if (unlikely(cur_seq32 > old_seq32 && after(old_seq32, cur_seq32)))
1027                 return cur_seq - (1LL << 32);
1028         return cur_seq;
1029 }
1030
1031 static void __mptcp_snd_una_update(struct mptcp_sock *msk, u64 new_snd_una)
1032 {
1033         msk->bytes_acked += new_snd_una - msk->snd_una;
1034         msk->snd_una = new_snd_una;
1035 }
1036
1037 static void ack_update_msk(struct mptcp_sock *msk,
1038                            struct sock *ssk,
1039                            struct mptcp_options_received *mp_opt)
1040 {
1041         u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt);
1042         struct sock *sk = (struct sock *)msk;
1043         u64 old_snd_una;
1044
1045         mptcp_data_lock(sk);
1046
1047         /* avoid ack expansion on update conflict, to reduce the risk of
1048          * wrongly expanding to a future ack sequence number, which is way
1049          * more dangerous than missing an ack
1050          */
1051         old_snd_una = msk->snd_una;
1052         new_snd_una = mptcp_expand_seq(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
1053
1054         /* ACK for data not even sent yet? Ignore.*/
1055         if (unlikely(after64(new_snd_una, snd_nxt)))
1056                 new_snd_una = old_snd_una;
1057
1058         new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd;
1059
1060         if (after64(new_wnd_end, msk->wnd_end))
1061                 msk->wnd_end = new_wnd_end;
1062
1063         /* this assumes mptcp_incoming_options() is invoked after tcp_ack() */
1064         if (after64(msk->wnd_end, READ_ONCE(msk->snd_nxt)))
1065                 __mptcp_check_push(sk, ssk);
1066
1067         if (after64(new_snd_una, old_snd_una)) {
1068                 __mptcp_snd_una_update(msk, new_snd_una);
1069                 __mptcp_data_acked(sk);
1070         }
1071         mptcp_data_unlock(sk);
1072
1073         trace_ack_update_msk(mp_opt->data_ack,
1074                              old_snd_una, new_snd_una,
1075                              new_wnd_end, msk->wnd_end);
1076 }
1077
1078 bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit)
1079 {
1080         /* Skip if DATA_FIN was already received.
1081          * If updating simultaneously with the recvmsg loop, values
1082          * should match. If they mismatch, the peer is misbehaving and
1083          * we will prefer the most recent information.
1084          */
1085         if (READ_ONCE(msk->rcv_data_fin))
1086                 return false;
1087
1088         WRITE_ONCE(msk->rcv_data_fin_seq,
1089                    mptcp_expand_seq(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
1090         WRITE_ONCE(msk->rcv_data_fin, 1);
1091
1092         return true;
1093 }
1094
1095 static bool add_addr_hmac_valid(struct mptcp_sock *msk,
1096                                 struct mptcp_options_received *mp_opt)
1097 {
1098         u64 hmac = 0;
1099
1100         if (mp_opt->echo)
1101                 return true;
1102
1103         hmac = add_addr_generate_hmac(msk->remote_key,
1104                                       msk->local_key,
1105                                       &mp_opt->addr);
1106
1107         pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
1108                  msk, hmac, mp_opt->ahmac);
1109
1110         return hmac == mp_opt->ahmac;
1111 }
1112
1113 /* Return false if a subflow has been reset, else return true */
1114 bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
1115 {
1116         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1117         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
1118         struct mptcp_options_received mp_opt;
1119         struct mptcp_ext *mpext;
1120
1121         if (__mptcp_check_fallback(msk)) {
1122                 /* Keep it simple and unconditionally trigger send data cleanup and
1123                  * pending queue spooling. We will need to acquire the data lock
1124                  * for more accurate checks, and once the lock is acquired, such
1125                  * helpers are cheap.
1126                  */
1127                 mptcp_data_lock(subflow->conn);
1128                 if (sk_stream_memory_free(sk))
1129                         __mptcp_check_push(subflow->conn, sk);
1130
1131                 /* on fallback we just need to ignore the msk-level snd_una, as
1132                  * this is really plain TCP
1133                  */
1134                 __mptcp_snd_una_update(msk, READ_ONCE(msk->snd_nxt));
1135
1136                 __mptcp_data_acked(subflow->conn);
1137                 mptcp_data_unlock(subflow->conn);
1138                 return true;
1139         }
1140
1141         mptcp_get_options(skb, &mp_opt);
1142
1143         /* The subflow can be in close state only if check_fully_established()
1144          * just sent a reset. If so, tell the caller to ignore the current packet.
1145          */
1146         if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
1147                 return sk->sk_state != TCP_CLOSE;
1148
1149         if (unlikely(mp_opt.suboptions != OPTION_MPTCP_DSS)) {
1150                 if ((mp_opt.suboptions & OPTION_MPTCP_FASTCLOSE) &&
1151                     msk->local_key == mp_opt.rcvr_key) {
1152                         WRITE_ONCE(msk->rcv_fastclose, true);
1153                         mptcp_schedule_work((struct sock *)msk);
1154                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFASTCLOSERX);
1155                 }
1156
1157                 if ((mp_opt.suboptions & OPTION_MPTCP_ADD_ADDR) &&
1158                     add_addr_hmac_valid(msk, &mp_opt)) {
1159                         if (!mp_opt.echo) {
1160                                 mptcp_pm_add_addr_received(sk, &mp_opt.addr);
1161                                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
1162                         } else {
1163                                 mptcp_pm_add_addr_echoed(msk, &mp_opt.addr);
1164                                 mptcp_pm_del_add_timer(msk, &mp_opt.addr, true);
1165                                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
1166                         }
1167
1168                         if (mp_opt.addr.port)
1169                                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_PORTADD);
1170                 }
1171
1172                 if (mp_opt.suboptions & OPTION_MPTCP_RM_ADDR)
1173                         mptcp_pm_rm_addr_received(msk, &mp_opt.rm_list);
1174
1175                 if (mp_opt.suboptions & OPTION_MPTCP_PRIO) {
1176                         mptcp_pm_mp_prio_received(sk, mp_opt.backup);
1177                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIORX);
1178                 }
1179
1180                 if (mp_opt.suboptions & OPTION_MPTCP_FAIL) {
1181                         mptcp_pm_mp_fail_received(sk, mp_opt.fail_seq);
1182                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILRX);
1183                 }
1184
1185                 if (mp_opt.suboptions & OPTION_MPTCP_RST) {
1186                         subflow->reset_seen = 1;
1187                         subflow->reset_reason = mp_opt.reset_reason;
1188                         subflow->reset_transient = mp_opt.reset_transient;
1189                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPRSTRX);
1190                 }
1191
1192                 if (!(mp_opt.suboptions & OPTION_MPTCP_DSS))
1193                         return true;
1194         }
1195
1196         /* we can't wait for recvmsg() to update the ack_seq, otherwise
1197          * monodirectional flows will stuck
1198          */
1199         if (mp_opt.use_ack)
1200                 ack_update_msk(msk, sk, &mp_opt);
1201
1202         /* Zero-data-length packets are dropped by the caller and not
1203          * propagated to the MPTCP layer, so the skb extension does not
1204          * need to be allocated or populated. DATA_FIN information, if
1205          * present, needs to be updated here before the skb is freed.
1206          */
1207         if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
1208                 if (mp_opt.data_fin && mp_opt.data_len == 1 &&
1209                     mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64))
1210                         mptcp_schedule_work((struct sock *)msk);
1211
1212                 return true;
1213         }
1214
1215         mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
1216         if (!mpext)
1217                 return true;
1218
1219         memset(mpext, 0, sizeof(*mpext));
1220
1221         if (likely(mp_opt.use_map)) {
1222                 if (mp_opt.mpc_map) {
1223                         /* this is an MP_CAPABLE carrying MPTCP data
1224                          * we know this map the first chunk of data
1225                          */
1226                         mptcp_crypto_key_sha(subflow->remote_key, NULL,
1227                                              &mpext->data_seq);
1228                         mpext->data_seq++;
1229                         mpext->subflow_seq = 1;
1230                         mpext->dsn64 = 1;
1231                         mpext->mpc_map = 1;
1232                         mpext->data_fin = 0;
1233                 } else {
1234                         mpext->data_seq = mp_opt.data_seq;
1235                         mpext->subflow_seq = mp_opt.subflow_seq;
1236                         mpext->dsn64 = mp_opt.dsn64;
1237                         mpext->data_fin = mp_opt.data_fin;
1238                 }
1239                 mpext->data_len = mp_opt.data_len;
1240                 mpext->use_map = 1;
1241                 mpext->csum_reqd = !!(mp_opt.suboptions & OPTION_MPTCP_CSUMREQD);
1242
1243                 if (mpext->csum_reqd)
1244                         mpext->csum = mp_opt.csum;
1245         }
1246
1247         return true;
1248 }
1249
1250 static void mptcp_set_rwin(struct tcp_sock *tp, struct tcphdr *th)
1251 {
1252         const struct sock *ssk = (const struct sock *)tp;
1253         struct mptcp_subflow_context *subflow;
1254         u64 ack_seq, rcv_wnd_old, rcv_wnd_new;
1255         struct mptcp_sock *msk;
1256         u32 new_win;
1257         u64 win;
1258
1259         subflow = mptcp_subflow_ctx(ssk);
1260         msk = mptcp_sk(subflow->conn);
1261
1262         ack_seq = READ_ONCE(msk->ack_seq);
1263         rcv_wnd_new = ack_seq + tp->rcv_wnd;
1264
1265         rcv_wnd_old = atomic64_read(&msk->rcv_wnd_sent);
1266         if (after64(rcv_wnd_new, rcv_wnd_old)) {
1267                 u64 rcv_wnd;
1268
1269                 for (;;) {
1270                         rcv_wnd = atomic64_cmpxchg(&msk->rcv_wnd_sent, rcv_wnd_old, rcv_wnd_new);
1271
1272                         if (rcv_wnd == rcv_wnd_old)
1273                                 break;
1274
1275                         rcv_wnd_old = rcv_wnd;
1276                         if (before64(rcv_wnd_new, rcv_wnd_old)) {
1277                                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICTUPDATE);
1278                                 goto raise_win;
1279                         }
1280                         MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICT);
1281                 }
1282                 return;
1283         }
1284
1285         if (rcv_wnd_new != rcv_wnd_old) {
1286 raise_win:
1287                 win = rcv_wnd_old - ack_seq;
1288                 tp->rcv_wnd = min_t(u64, win, U32_MAX);
1289                 new_win = tp->rcv_wnd;
1290
1291                 /* Make sure we do not exceed the maximum possible
1292                  * scaled window.
1293                  */
1294                 if (unlikely(th->syn))
1295                         new_win = min(new_win, 65535U) << tp->rx_opt.rcv_wscale;
1296                 if (!tp->rx_opt.rcv_wscale &&
1297                     READ_ONCE(sock_net(ssk)->ipv4.sysctl_tcp_workaround_signed_windows))
1298                         new_win = min(new_win, MAX_TCP_WINDOW);
1299                 else
1300                         new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
1301
1302                 /* RFC1323 scaling applied */
1303                 new_win >>= tp->rx_opt.rcv_wscale;
1304                 th->window = htons(new_win);
1305                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDSHARED);
1306         }
1307 }
1308
1309 __sum16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum)
1310 {
1311         struct csum_pseudo_header header;
1312         __wsum csum;
1313
1314         /* cfr RFC 8684 3.3.1.:
1315          * the data sequence number used in the pseudo-header is
1316          * always the 64-bit value, irrespective of what length is used in the
1317          * DSS option itself.
1318          */
1319         header.data_seq = cpu_to_be64(data_seq);
1320         header.subflow_seq = htonl(subflow_seq);
1321         header.data_len = htons(data_len);
1322         header.csum = 0;
1323
1324         csum = csum_partial(&header, sizeof(header), sum);
1325         return csum_fold(csum);
1326 }
1327
1328 static __sum16 mptcp_make_csum(const struct mptcp_ext *mpext)
1329 {
1330         return __mptcp_make_csum(mpext->data_seq, mpext->subflow_seq, mpext->data_len,
1331                                  ~csum_unfold(mpext->csum));
1332 }
1333
1334 static void put_len_csum(u16 len, __sum16 csum, void *data)
1335 {
1336         __sum16 *sumptr = data + 2;
1337         __be16 *ptr = data;
1338
1339         put_unaligned_be16(len, ptr);
1340
1341         put_unaligned(csum, sumptr);
1342 }
1343
1344 void mptcp_write_options(struct tcphdr *th, __be32 *ptr, struct tcp_sock *tp,
1345                          struct mptcp_out_options *opts)
1346 {
1347         const struct sock *ssk = (const struct sock *)tp;
1348         struct mptcp_subflow_context *subflow;
1349
1350         /* Which options can be used together?
1351          *
1352          * X: mutually exclusive
1353          * O: often used together
1354          * C: can be used together in some cases
1355          * P: could be used together but we prefer not to (optimisations)
1356          *
1357          *  Opt: | MPC  | MPJ  | DSS  | ADD  |  RM  | PRIO | FAIL |  FC  |
1358          * ------|------|------|------|------|------|------|------|------|
1359          *  MPC  |------|------|------|------|------|------|------|------|
1360          *  MPJ  |  X   |------|------|------|------|------|------|------|
1361          *  DSS  |  X   |  X   |------|------|------|------|------|------|
1362          *  ADD  |  X   |  X   |  P   |------|------|------|------|------|
1363          *  RM   |  C   |  C   |  C   |  P   |------|------|------|------|
1364          *  PRIO |  X   |  C   |  C   |  C   |  C   |------|------|------|
1365          *  FAIL |  X   |  X   |  C   |  X   |  X   |  X   |------|------|
1366          *  FC   |  X   |  X   |  X   |  X   |  X   |  X   |  X   |------|
1367          *  RST  |  X   |  X   |  X   |  X   |  X   |  X   |  O   |  O   |
1368          * ------|------|------|------|------|------|------|------|------|
1369          *
1370          * The same applies in mptcp_established_options() function.
1371          */
1372         if (likely(OPTION_MPTCP_DSS & opts->suboptions)) {
1373                 struct mptcp_ext *mpext = &opts->ext_copy;
1374                 u8 len = TCPOLEN_MPTCP_DSS_BASE;
1375                 u8 flags = 0;
1376
1377                 if (mpext->use_ack) {
1378                         flags = MPTCP_DSS_HAS_ACK;
1379                         if (mpext->ack64) {
1380                                 len += TCPOLEN_MPTCP_DSS_ACK64;
1381                                 flags |= MPTCP_DSS_ACK64;
1382                         } else {
1383                                 len += TCPOLEN_MPTCP_DSS_ACK32;
1384                         }
1385                 }
1386
1387                 if (mpext->use_map) {
1388                         len += TCPOLEN_MPTCP_DSS_MAP64;
1389
1390                         /* Use only 64-bit mapping flags for now, add
1391                          * support for optional 32-bit mappings later.
1392                          */
1393                         flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
1394                         if (mpext->data_fin)
1395                                 flags |= MPTCP_DSS_DATA_FIN;
1396
1397                         if (opts->csum_reqd)
1398                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1399                 }
1400
1401                 *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
1402
1403                 if (mpext->use_ack) {
1404                         if (mpext->ack64) {
1405                                 put_unaligned_be64(mpext->data_ack, ptr);
1406                                 ptr += 2;
1407                         } else {
1408                                 put_unaligned_be32(mpext->data_ack32, ptr);
1409                                 ptr += 1;
1410                         }
1411                 }
1412
1413                 if (mpext->use_map) {
1414                         put_unaligned_be64(mpext->data_seq, ptr);
1415                         ptr += 2;
1416                         put_unaligned_be32(mpext->subflow_seq, ptr);
1417                         ptr += 1;
1418                         if (opts->csum_reqd) {
1419                                 /* data_len == 0 is reserved for the infinite mapping,
1420                                  * the checksum will also be set to 0.
1421                                  */
1422                                 put_len_csum(mpext->data_len,
1423                                              (mpext->data_len ? mptcp_make_csum(mpext) : 0),
1424                                              ptr);
1425                         } else {
1426                                 put_unaligned_be32(mpext->data_len << 16 |
1427                                                    TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1428                         }
1429                         ptr += 1;
1430                 }
1431
1432                 /* We might need to add MP_FAIL options in rare cases */
1433                 if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions))
1434                         goto mp_fail;
1435         } else if (OPTIONS_MPTCP_MPC & opts->suboptions) {
1436                 u8 len, flag = MPTCP_CAP_HMAC_SHA256;
1437
1438                 if (OPTION_MPTCP_MPC_SYN & opts->suboptions) {
1439                         len = TCPOLEN_MPTCP_MPC_SYN;
1440                 } else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions) {
1441                         len = TCPOLEN_MPTCP_MPC_SYNACK;
1442                 } else if (opts->data_len) {
1443                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
1444                         if (opts->csum_reqd)
1445                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1446                 } else {
1447                         len = TCPOLEN_MPTCP_MPC_ACK;
1448                 }
1449
1450                 if (opts->csum_reqd)
1451                         flag |= MPTCP_CAP_CHECKSUM_REQD;
1452
1453                 if (!opts->allow_join_id0)
1454                         flag |= MPTCP_CAP_DENY_JOIN_ID0;
1455
1456                 *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
1457                                       MPTCP_SUPPORTED_VERSION,
1458                                       flag);
1459
1460                 if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
1461                     opts->suboptions))
1462                         goto mp_capable_done;
1463
1464                 put_unaligned_be64(opts->sndr_key, ptr);
1465                 ptr += 2;
1466                 if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
1467                         goto mp_capable_done;
1468
1469                 put_unaligned_be64(opts->rcvr_key, ptr);
1470                 ptr += 2;
1471                 if (!opts->data_len)
1472                         goto mp_capable_done;
1473
1474                 if (opts->csum_reqd) {
1475                         put_len_csum(opts->data_len,
1476                                      __mptcp_make_csum(opts->data_seq,
1477                                                        opts->subflow_seq,
1478                                                        opts->data_len,
1479                                                        ~csum_unfold(opts->csum)),
1480                                      ptr);
1481                 } else {
1482                         put_unaligned_be32(opts->data_len << 16 |
1483                                            TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1484                 }
1485                 ptr += 1;
1486
1487                 /* MPC is additionally mutually exclusive with MP_PRIO */
1488                 goto mp_capable_done;
1489         } else if (OPTIONS_MPTCP_MPJ & opts->suboptions) {
1490                 if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
1491                         *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1492                                               TCPOLEN_MPTCP_MPJ_SYN,
1493                                               opts->backup, opts->join_id);
1494                         put_unaligned_be32(opts->token, ptr);
1495                         ptr += 1;
1496                         put_unaligned_be32(opts->nonce, ptr);
1497                         ptr += 1;
1498                 } else if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
1499                         *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1500                                               TCPOLEN_MPTCP_MPJ_SYNACK,
1501                                               opts->backup, opts->join_id);
1502                         put_unaligned_be64(opts->thmac, ptr);
1503                         ptr += 2;
1504                         put_unaligned_be32(opts->nonce, ptr);
1505                         ptr += 1;
1506                 } else {
1507                         *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1508                                               TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
1509                         memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
1510                         ptr += 5;
1511                 }
1512         } else if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
1513                 u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
1514                 u8 echo = MPTCP_ADDR_ECHO;
1515
1516 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1517                 if (opts->addr.family == AF_INET6)
1518                         len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
1519 #endif
1520
1521                 if (opts->addr.port)
1522                         len += TCPOLEN_MPTCP_PORT_LEN;
1523
1524                 if (opts->ahmac) {
1525                         len += sizeof(opts->ahmac);
1526                         echo = 0;
1527                 }
1528
1529                 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1530                                       len, echo, opts->addr.id);
1531                 if (opts->addr.family == AF_INET) {
1532                         memcpy((u8 *)ptr, (u8 *)&opts->addr.addr.s_addr, 4);
1533                         ptr += 1;
1534                 }
1535 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1536                 else if (opts->addr.family == AF_INET6) {
1537                         memcpy((u8 *)ptr, opts->addr.addr6.s6_addr, 16);
1538                         ptr += 4;
1539                 }
1540 #endif
1541
1542                 if (!opts->addr.port) {
1543                         if (opts->ahmac) {
1544                                 put_unaligned_be64(opts->ahmac, ptr);
1545                                 ptr += 2;
1546                         }
1547                 } else {
1548                         u16 port = ntohs(opts->addr.port);
1549
1550                         if (opts->ahmac) {
1551                                 u8 *bptr = (u8 *)ptr;
1552
1553                                 put_unaligned_be16(port, bptr);
1554                                 bptr += 2;
1555                                 put_unaligned_be64(opts->ahmac, bptr);
1556                                 bptr += 8;
1557                                 put_unaligned_be16(TCPOPT_NOP << 8 |
1558                                                    TCPOPT_NOP, bptr);
1559
1560                                 ptr += 3;
1561                         } else {
1562                                 put_unaligned_be32(port << 16 |
1563                                                    TCPOPT_NOP << 8 |
1564                                                    TCPOPT_NOP, ptr);
1565                                 ptr += 1;
1566                         }
1567                 }
1568         } else if (unlikely(OPTION_MPTCP_FASTCLOSE & opts->suboptions)) {
1569                 /* FASTCLOSE is mutually exclusive with others except RST */
1570                 *ptr++ = mptcp_option(MPTCPOPT_MP_FASTCLOSE,
1571                                       TCPOLEN_MPTCP_FASTCLOSE,
1572                                       0, 0);
1573                 put_unaligned_be64(opts->rcvr_key, ptr);
1574                 ptr += 2;
1575
1576                 if (OPTION_MPTCP_RST & opts->suboptions)
1577                         goto mp_rst;
1578                 return;
1579         } else if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions)) {
1580 mp_fail:
1581                 /* MP_FAIL is mutually exclusive with others except RST */
1582                 subflow = mptcp_subflow_ctx(ssk);
1583                 subflow->send_mp_fail = 0;
1584
1585                 *ptr++ = mptcp_option(MPTCPOPT_MP_FAIL,
1586                                       TCPOLEN_MPTCP_FAIL,
1587                                       0, 0);
1588                 put_unaligned_be64(opts->fail_seq, ptr);
1589                 ptr += 2;
1590
1591                 if (OPTION_MPTCP_RST & opts->suboptions)
1592                         goto mp_rst;
1593                 return;
1594         } else if (unlikely(OPTION_MPTCP_RST & opts->suboptions)) {
1595 mp_rst:
1596                 *ptr++ = mptcp_option(MPTCPOPT_RST,
1597                                       TCPOLEN_MPTCP_RST,
1598                                       opts->reset_transient,
1599                                       opts->reset_reason);
1600                 return;
1601         }
1602
1603         if (OPTION_MPTCP_PRIO & opts->suboptions) {
1604                 subflow = mptcp_subflow_ctx(ssk);
1605                 subflow->send_mp_prio = 0;
1606
1607                 *ptr++ = mptcp_option(MPTCPOPT_MP_PRIO,
1608                                       TCPOLEN_MPTCP_PRIO,
1609                                       opts->backup, TCPOPT_NOP);
1610
1611                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPPRIOTX);
1612         }
1613
1614 mp_capable_done:
1615         if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
1616                 u8 i = 1;
1617
1618                 *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
1619                                       TCPOLEN_MPTCP_RM_ADDR_BASE + opts->rm_list.nr,
1620                                       0, opts->rm_list.ids[0]);
1621
1622                 while (i < opts->rm_list.nr) {
1623                         u8 id1, id2, id3, id4;
1624
1625                         id1 = opts->rm_list.ids[i];
1626                         id2 = i + 1 < opts->rm_list.nr ? opts->rm_list.ids[i + 1] : TCPOPT_NOP;
1627                         id3 = i + 2 < opts->rm_list.nr ? opts->rm_list.ids[i + 2] : TCPOPT_NOP;
1628                         id4 = i + 3 < opts->rm_list.nr ? opts->rm_list.ids[i + 3] : TCPOPT_NOP;
1629                         put_unaligned_be32(id1 << 24 | id2 << 16 | id3 << 8 | id4, ptr);
1630                         ptr += 1;
1631                         i += 4;
1632                 }
1633         }
1634
1635         if (tp)
1636                 mptcp_set_rwin(tp, th);
1637 }
1638
1639 __be32 mptcp_get_reset_option(const struct sk_buff *skb)
1640 {
1641         const struct mptcp_ext *ext = mptcp_get_ext(skb);
1642         u8 flags, reason;
1643
1644         if (ext) {
1645                 flags = ext->reset_transient;
1646                 reason = ext->reset_reason;
1647
1648                 return mptcp_option(MPTCPOPT_RST, TCPOLEN_MPTCP_RST,
1649                                     flags, reason);
1650         }
1651
1652         return htonl(0u);
1653 }
1654 EXPORT_SYMBOL_GPL(mptcp_get_reset_option);